1. Field of the Invention
The present invention relates to high impact resistant polycarbonate, a process for producing said polycarbonate, and a polycarbonate resin composition. More particularly, it relates to a novel high impact resistant polycarbonate resin having cumylphenoxy group as terminal group(s), a viscosity average molecular weight of at least 10,000 and an acetone soluble content of not more than 3.5% by weight; a process for efficiently producing said polycarbonate resin; and a polycarbonate resin composition which is of high fluidity and has high impact resistance, and is rarely subject to a reduction in molecular weight during molding thereof.
2. Description of Related Art
A process for producing polycarbonate using cumylphenol as a terminator or polymerization modifier has heretofore been known, as described in Japanese Patent Application Laid-Open No. 20993/1976. The polycarbonate produced by this process, however, suffers from a disadvantage in that impact resistance is not sufficiently high, because it is produced by the conventional process with no special modifications except that cumylphenol is used as a terminator.
As a result of extensive investigations, it has been found that the polycarbonate produced by the process described in Japanese Patent Application Laid-Open No. 20993/1976, has the acetone soluble content of 3.5% by weight or more, which is mainly responsible for a reduction in impact resistance.
Based on the above findings, further investigations have been made to develop polycarbonate which is excellent in impact resistance. As a result, it has been found that if a polycarbonate oligomer and bisphenol A as polymerization starting materials and cumylphenol as a terminator are first reacted under the turbulent flow condition and, thereafter, an aqueous solution of alkali hydroxide is added thereto and the resulting mixture is further reacted under the laminar flow condition, there can be obtained novel polycarbonate which has a decreased acetone soluble content and is of improved impact resistance.
Polycarbonate is generally excellent in heat resistance, mechanical characteristics (particularly impact resistance), optical characteristics and electrical characteristics, and further is low in shrinkage during molding because it is an amorphous polymer. Thus it has been widely used in production of electric parts, illumination devices, OA (office automation) devices, construction materials, automobile parts, and so forth, particularly as a typical engineering plastic material.
A molding of polycarbonate has to be carried out at elevated temperatures. During this molding, therefore, the carbonate bond in the polymer main chain undergoes decomposition, and the polycarbonate is inevitably colored and subject to a reduction in mechanical strength. Particularly in molding of an article which is thin in wall or is in a complicated shape, especially high temperature is needed to lower the melt viscosity and thus the polycarbonate is subject to serious thermal deterioration.
In order to overcome the above problem, an antioxidant has been added to polycarbonate. However, if antioxidants other than phosphorus-based antioxidants are used, coloration cannot be prevented, and even if phosphorus-based antioxidants are used, a sufficiently high mechanical strength, particularly a sufficiently high impact resistance at low temperatures cannot be obtained.
Moreover, in order to permit molding in a complicated shape, a lubricant has been added. Addition of a lubricant, however, causes a reduction in molecular weight during molding, thereby decreasing the mechanical strength.
It has therefore been desired to overcome the above problems. As a result of investigations, it has been found that when a specified amount of a phosphorus-based antioxidant is added to a polycarbonate resin produced using cumylphenol as a polymerization modifier, a high mechanical strength is unexpectedly obtained, and even if a lubricant is added, the mechanical strength is maintained without a reduction of molecular weight.